Abstract

Lotus corniculatus containing 23 g/kg DM of extractable condensed tannin (CT) and 35 g total CT/kg DM was fed to sheep in two experiments. In both experiments half the sheep received supplementation with polyethylene glycol (PEG), which binds and inactivates CT, enabling the effects of CT to be quantified by comparing control sheep (CT operating) with PEG sheep (CT inactivated). Experiment 1 was conducted indoors, with sheep held in metabolism crates and fed hourly to determine the effects of CT upon apparent digestibility and upon plasma irreversible loss (IRL) rates of methionine, cystine and inorganic sulphate, using 35S labelling. Experiment 2 as a field trial with weaned lambs given a restricted allowance of either lotus corniculatus (CT-containing) or lucerne (non CT-containing), with or without PEG supplementation. In Experiment 1, CT slightly lowered the apparent digestibility of organic matter (0.77 vs 0.80; P<0.1), hemicellulose (0.61 vs 0.67; P=0.118) and markedly reduced nitrogen apparent digestibility (0.72 vs 0.80; P<0.01), but had no effect upon cellulose digestibility. CT increased the IRL of plasma cystine (13.1 vs 7.0 mmol/min; P<0.05) and reduced the IRL of plasma inorganic sulphate (36.8 vs 48.1 mmol/min; P<0.01) but had no effect upon plasma methionine IRL. In Experiment 2, live weight gain and wool growth were similar for sheep grazing lucerne (with and without PEG supplementation) and for sheep grazing lotus with PEG supplementation. In sheep grazing lotus, action of CT increased wool production (12.1 vs 10.9 g/d; P<0.05) and slightly increased live weight gain (203 vs 188 g/d; P=0.07). These experiments showed that CT in Lotus corniculatus increased the amount of cystine available for body synthetic reactions and increased wool growth.

Y, Wang, GC Waghorn, GB Douglas, TN Barry, and GF Wilson

Proceedings of the New Zealand Society of Animal Production, Volume 54, , 219-222, 1994